The optimum laser source for performing coronary artery laser angioplasty has not been determined. The purpose of this study is to define the most suitable laser source for vaporization of atherosclerotic plaque. Selected coronary arteries from human cadavers are exposed to lasers of various wave lengths and precise real time measurements of thermal diffusion are made by thermocouples and infra-red photography. In addition well defined gross and histopathological techniques are used to compare the effects of various laser-tissue interactions. Three laser sources have been tested of which one appears useful for the proposed application.